This tutorial is valid for Opera 9 or above; but previous versions might work.

In the menu bar, go to Tools > Mail and chat accounts...
Click on Add...
Make sure Regular e-mail (POP) is selected. (It should be by default.) Click Next >.

In this section, you see three fields: Real Name, E-mail address, and Organization.
Organization is optional. Type in your name in the Real Name field, and your account's e-mail in the E-mail address field (syntax: cpanel_username@your_subdomain.trap17.com). Click Next >.

In this section, in the Login name field, type in your C-panel username. And in the Password field, your C-panel password. Click Next >.

In this section everything should be filled out automatically for you, and all you'd have to do is click Finish.

After clicking Finish, Opera's Mail Client will attempt to gather any mail you have in your Inbox for your account.

Hope this provides some convenience for those who use their account's e-mail, and who love to use Opera.

Your tutorial is quite useful. The only problem was that I had to add the domin after my email user name. Other wise everything went flwlessly. People should make more tutorials like this one.